The mass production of vehicle seating units is commonly carried out by welding together the bottom and back rest portions of a seat frame, mounting contoured foam cushions, typically open cell plastic, on the frame and thereafter fitting trim components to the cushions. Such trim components may, in the illustrative case of a single occupant bucket seat, involve a bag-like seat back cover and a seat cushion cover. Both may be fabricated of vinyl, leather, woven fabric, synthetic fabric, or a combination. The application of the trim components unifies the seating unit by securing the foam cushions to the seat frame. Such cushions may also be partly or fully secured to the seal frame by other means such as the use of adhesives.
The step of securing the trim components to the seal frame is often a strenuous one for the assembly worker. To produce an attractive, well-made seat the trim must be stretched taut over the cushions and held in place while hog rings or staples are applied with the use of an automatic, commercially-available gun. This operation is usually performed with the seat in an inverted position. The seat must be reoriented several times during the operation. These operations, while manageable, are repetitive and can result in worker fatigue and physiological ailments associated with repetitive stress to the muscles, tendons and ligaments of the arms and hands. A machine which partially assists in the application of a seat back cover to a preassembled seat frame/back cushion assembly is disclosed in U.S. Pat. No. 4,385,427 "Machine for Installing Upholstery Covers," issued May 31, 1983 to Frederick F. Fraiser. The disclosure of that patent is incorporated herein by reference.